Ribbon feeding and reversing mechanism

ABSTRACT

A ribbon is advanced through a ribbon fork and wound alternately onto a pair of spools which are mounted on a carriage for movement with a single print element. The spools are carried on ratchet wheels which are rotatably driven in opposite directions by a pair of corresponding indexing pawls which are resiliently urged into engagement with the ratchet wheels and undergo an oscillatory movement with each actuation of a type key action, and the rotation of the ratchet wheels is determined by a control member which is movable to alternate positions for reversing the winding of the ribbon on the pair of spools. The control member has a pair of arms for engaging the indexing pawls and each of the arms carries a lock pawl for engaging a ratchet wheel. Upon movement of the control member to an alternate position to enable an indexing pawl to rotate a ratchet wheel, the lock pawl of the corresponding arm engages the ratchet wheel to prevent rotational movement opposite to the winding of the ribbon while the other arm removes the other indexing pawl from engagement with the other ratchet wheel. When the ribbon becomes fully wound onto the spool, the direction of winding is reversed to the other spool by the operation of a lever sensing the tension in the ribbon and moving the disengaged yet oscillating indexing pawl to a position for shifting the control member to the other alternate position.

United States Patent Decker [4 1 Sept. 23, 1975 RIBBON FEEDING AND REVERSING MECHANISM [75] Inventor: Herbert Decker, Lauf, Germany [73] Assignee: Triumph Werke Nurnberg A.G.,

Nurnberg, Germany [22] Filed: May 10, 1973 [21] Appl. No.: 359,130

[30] Foreign Application Priority Data May 16, 1972 Germany 2223757 [52] US. Cl. 197/162 [51] Int. Cl B41j 33/46 [58] Field of Search 197/151, 160, 161, 162, 197/163, 164, 165

[56] References Cited UNITED STATES PATENTS 609,476 8/1898 Stickney 197/163 896,825 8/1908 Hart 197/160 917,246 4/1909 Callam 197/160 940,814 11/1909 Kuntzler. 197/160 1,065,531 6/1913 Kavle 197/165 1,798,583 3/1931 Bishop et al. 197/162 X 2,282,994 5/1942 Dobs0n.... 197/165 2,902,136 9/1959 Whippo 197/165 3,513,957 5/1970 Ricciardi et al. 197/151 3,532,204 10/1970 Sasaki 197/165 X 3,602,353 8/1971 Chvatlinsky et al. 197/161 Primary Examiner-Ernest T. Wright, Jr. Attorney, Agent, or Firm-Joseph R. Spalla [5 7] ABSTRACT A ribbon is advanced through a ribbon fork and wound alternately onto a pair of spools which are mounted on a carriage for movement with a single print element. The spools are carried on ratchet wheels which are rotatably driven in opposite directions by a pair of corresponding indexing pawls which are resiliently urged into engagement with the ratchet wheels and undergo an oscillatory movement with each actuation of a type key action, and the rotation of the ratchet wheels is determined by a control member which is movable to alternate positions for reversing the winding of the ribbon on the pair of spools. The control member has a pair of arms for engaging the indexing pawls and each of the arms carries a lock pawl for engaging a ratchet wheel. Upon movement of the control member to an alternate position to enable an indexing pawl to rotate a ratchet wheel, the lock pawl of the corresponding arm engages the ratchet wheel to prevent rotational movement opposite to the winding of the ribbon while the other arm removes the other indexing pawl from engagement with the other ratchet wheel. When the ribbon becomes fully wound onto the spool, the direction of winding is reversed to the other spool by the operation of a lever sensing the tension in the ribbon and moving the disengaged yet oscillating indexing pawl to a position for shifting the control member to the other alternate position.

1 Claim, 4 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of3 3,907,094

US Patent Sept. 23,1975 Sheet 2. of3 3,907,094

Sheet 3 of 3 Sept. 23,1975

US Patent RIBBON FEEDING AND REVERSING MECHANISM This invention relates to a ribbon winding mechanism for a single element typewriter, and more particularly to a typewriter mechanism for reversibly winding a ribbon on a pair of spools. I

In a typewriter, printing is effected by impacting a selected type character against a recording medium located on a platen, and with each successive printing operation a ribbon is positioned adjacent the platen for enabling the impacting type character to r'na'rk the re cording medium and the ribbon is advanced an incremental length to prevent successive impacting of the same ribbon portion. Typically, the ribbon is unwound from a spool and advanced past the platen by winding onto another spool, and after the ribbon isfully wound onto the other spool the winding is reversed so as to achieve greater utilization of the ribbon.

A number of ribbon feeding mechanisms have been provided for use with a segmented typewriter in'which the type characters are carried by a plurality of type bars and impacted at a common print point. In such a typewriter, the ribbon feeding mechanism is stationary with the ribbon spools located on opposite sides of the typewriter frame. However, such ribbon feeding arrangements are impractical for a single element typewriter wherein thetype characters are formed on a print element which is movable along a stationary platen, because the ribbon feeding mechanism must move along the platen with the print element.

The ribbon feeding arrangements which have been provided for single element typewriters in the'past are shown, for example, in German published application DT-PS 1,216,890 and Us. Pat, No. 2,902,136. In these arrangements, a pair of ribbon spools are rotatably driven by a single indexing pawl undergoing anoscillatable movement with each printing operation. A pair of lock pawls for preventing rotation of the spools opposite to the winding movement are carried on a pivotal lock member which is resiliently connected to the indexing pawl, and the ribbon has special reinforcements near each end for engaging tension arms which move a control member to alternate operating positionsfor reversing the winding of the ribbon onto the, other spool. The movement of the control member to an alternate position pivots the lock member which in turn resiliently urges the indexing pawl to rotatably drive the other ribbon spool. However, such an arrangement is disadvantageous because of its complexity and the number of parts involved along with the need for a ribbon having special reinforcements for acting on the tension arms. 1

Accordingly, an object of the present invention is to provide a ribbon feeding arrangementfor a single element typewriter which minimizes the number of parts and is usablewith ordinary commercially available ribbons without special reinforcements.

Another object of the present invention is to provide a ribbon feeding reversal mechanism wherein the control member and the locking pawls are formed as a single integral part.

Still other objects, features and advantages of the present invention will become apparent to those skilled in the art from a reading of the following detaileddescription of the invention, taken in conjunction with the accompanying drawing, wherein:

FIG. 1 is a perspective view of a ribbon feeding reversing mechanism constructed in accordance with the present invention;

FIG. '2 is a partial perspective view of the ribbon feeding arrangement shown in FIG. 1 and illustrating the manner in which the indexing pawls are supported and moved;..

FIG. 3 is a top view of the ribbon feeding mechanism for a single element typewriter shown in FIG. 1; and

FIG. 4 is a side elevational view of the ribbon feeding mechanism of FIG. 1. v Referring now in detail to the figures in the drawing, there is shown a typewriter printing arrangement, generally indicated .11, for printing type characters or other symbols on a recording medium, not shown, which may be desirably located on a platen 13. As is conventional, the type characters 15 to be printed are formed ona generally spherical element 17 which undergoes a printing movement with each actuation of a type key action to impact a selected type character 15 against the platen 13. To effect the printing of the selected type character 15, a typewriter ribbon 19 is carried in .aribbon vibrator 12 and moved to a printing lo.- cation adjacent the platen 13 prior to the impactingof the type character 15 against the platen 13 for enabling the recording medium to be marked. The printing arrangement 11 is mounted on a carriage 23 for movement along the platen 13 to print a line of type, and with each successive printing operation the ribbon 19 is advanced an incremental length. through the ribbon vibrator 21 by a ribbon feed mechanism, generally indicated 25,.as willbe discussed below. The ribbon 19 is secured at its ends to a pair of spools 27L, 27R and wound thereon with each o'fthe spools 27L, 27R alternately serving as supply and take-up spools, and the spools 27L, 27R are mounted on the carriage 23 for movement along. the platen 13 with the spherical element 17-. When-the ribbon I9 is fully wound onto one of thespools 27L, 27R, for example the spool 27L, a ribbon reversing means, generally indicated '29, acts on the ribbon feed mechanism 25, as will also be explained below, to alternate the winding of the ribbon 19 onto the other spool 27R. The recording medium, as well as other portions of the typewriter printing arrangement 11 are not shown, since they form no part of the present invention and maybe desirably conventional.

' .As shown, the carriage 23 is supported for movement along the platen 13 by a shaft 31 which is sliclably received through an opening 33 in the wall of the carriage 23 anda support member 37 which is suitably attached tothe wall 35 of the carriage 23 and slidably received by a U-shaped rail 39 which maybe secured to the frame of the typewriter. The ribbon spools 27L, 27R

are supported on an L-shaped bracket 41 which is secured to the wall 35 of the carriage 23 by suitable means, for example bolts 43, and the spools 27L, 27R are carried on a pair of corresponding ratchet wheels 45L, 45R which are supported for rotation by axial shafts 47L '(FIG. 4), 47R (not shown) journaled in the tom side of the. bracket 41. .As is conventional, the

spools 27L, 27R are mounted on the ratchet wheels 45L, 45R for rotation therewith, and each of the ratchet wheels 45L, 45R have spindles 53L, 53R respectively which are received in axial openings. not shown, of the spools 27L, 27R and drive pins 55L, 55R respectively which are radially spaced from the axial spindles 53L, 53R and suitably received in the spools 27L, 27R. To enable the spools 27L, 27R to be rotatably driven, the ratchet wheels 45L, 45R have teeth formed on the periphery for engagement by corresponding indexing pawls 57L, 57R respectively which form a portion of the ribbon feed mechanism 25.

To advance the ribbon 19 through the ribbon fork 49 with each actuation to a type key action, the indexing pawls 57L, 57R are driven in an oscillatory movement for engaging and rotating one of the ratchet wheels 45L, 45R. As more particularly shown in FIGS. 2 and 4, the indexing pawls 57L, 57R are mounted on a drive member 59 which is located beneath the bracket 41 and undergoes an oscillatory movement in response to the rotational movement of an eccentric cam 61. The indexing pawls 57L, 57R are pivotally supported on a rod 63 carried by the drive member 59 and project upwardly through openings 65L, 65R in the bracket 41 for engaging the ratchet wheels 45L, 45R. Each of the indexing pawls 57L, 57R have a forward extension 67L, 67R for engaging the bottom side of the bracket 41, and the indexing pawls 57L, 57R are urged axially along the rod 63 and upwardly against the bracket 41' toward engagement with the ratchet wheels 45L, 45R by a pair of springs 69L, 69R, each coiled about the rod 63 with one end secured to the indexing pawls 57L, 57R and the other end secured to the drive member 59. The drive member 59 is pivotally supported on the carriage 23 and resiliently urged into engagement with the eccentric cam 61 by a spring 71 stretched between the drive member 59 and the carriage 23, and the eccentric cam 61 is keyed to a drive shaft 73 which undergoes a single revolution with each actuation of a type key action. To drive the indexing pawls 57L, 57R in a succession of oscillatory movements as the carriage 23 moves along the platen 13 to print a line of type, the eccentric cam 61 is slidable along the drive shaft 73 in accordance with the movement of the carriage 23, and the drive shaft 73 is received through a suitable opening, not shown, in the wall 35 of the carriage 23.

As discussed above, the ribbon spools 27L, 27R serve alternately as take-up and supply spools, and the alternate winding of the ribbon 19 is effected by a control member 75 which forms a portion of the ribbon reversing means 29 and controls the engagement of the indexing pawls 57L, 57R with the corresponding ratchet wheels 45L, 45R. As more particularly shown in FIGS. 1 and 3, the control member 75 is pivotally supported on the bracket 41 as at pivot pin 76 and has a pair of arms 77L, 77R associated with the pair of ratchet wheels 45L, 45R and terminating in upright lock pawls 79L, 79R for engagement with the corresponding ratchet wheels 45L, 45R. The indexing pawls 57L, 57R are received between the arms 77L, 77R of the control member 75 which provide guide surfaces 778 for engaging the indexing pawls 57L, 57R, and the control member 75 is pivotally movable to alternate positions for alternating the oscillatable engagement of the indexing pawls 57L, 57R with the ratchet wheels 45L, 45RfUpon movement to one alternate position to effect winding of the ribbon 19 on the spool 27L, the lock pawl 79L of one arm 77L engages the associated ratchet wheel 45L while guide surface 775 of the other arm 77R guides the other indexing pawl 57R from engagement with the other ratchet wheel 45R. Likewise,

upon movement to the other alternate position to effect winding of the ribbon 19 on the spool 27R, the lock pawl 79R of the other arm 77R engages the other ratchet wheel 45R while guide surface 775 of the arm 77L guides the indexing pawl 57L from engagement with the other ratchet wheel 45L. The control member is held at the alternate positions by a detent arrangement, generally indicated 81. As shown, the detent arrangement 81 includes another arm 83 of the control member 75 which extends through an opening 85 in the bracket 41 and is resiliently urged to the alternate positions by a spring 87 compressed between the arm 83 and a suitable portion of the bracket 41.

In the operation of the typewriter printing arrangement 1 1, the ribbon 19 is advanced through the ribbon fork 49 and the tension arms 51L, 51R by the indexing pawls 57L, 57R which undergo an oscillatory movement in response to each successive actuation of a type key action. With the control member 75 in the alternate position shown in FIGS. 1 and 3, the ribbon 19 is wound onto the spool 27L by the engagement of the indexing pawl 57L with the ratchet wheel 45L, which is prevented from rotating in a direction reverse to the winding movementby the lock pawl 79L carried by the arm 77 L of the control member 75. The other indexing pawl 57R slides along the guide surface 775 provided by the other arm 77R of the control member 75 which prevents engagement with the other ratchet wheel 45R and maintains the other lock pawl 79R disengaged. The ribbon 19 is maintained taut during the winding movement by a pair of drag levers 89L, 89R urged against the ribbon 19 wound on the spools 27L, 27R and the tautness of the ribbon 19 is sensed by the tension arms 51L, 51R which are operable, in a manner to be explained below, to effect a reversal of the winding of the ribbon 19. As shown, the drag levers 89L, 89R are pivotally supported about a common post 91 and urged against the ribbon 19 wound on the spools 27L, 27R by a spring 93 stretched between the drag levers 89L, 89R and around the post 91. As more particularly shown in FIGS. 1 and 3, the tension arms 51L, 51R extend between the axial shafts 47L, 47R of the corresponding ratchet wheels 45L, 45R and are urged thereagainst by springs 95L, 95R stretched between the tension arms 51L, 51R and the bracket 41.

As the ribbon 19 becomes fully wound on the ribbon spool 27L, the tension in the ribbon 19 increases due to the continued advancement of the ribbon 19 through the ribbon fork 49, and the ribbon 19 acts on the tension lever 51R associated with the spool 27R to pivot the tension lever 51R against the urging of the spring 95R. The tension lever 51R has an arcuate portion 80 curved about the axial shaft 47R of the ratchet wheel 45R, and the pivoting of the tension lever 51R brings the arcuate portion 80 of the tension lever 51R into engagement with the forward projection 67R of the indexing pawl 57R so as to move the indexing pawl 57R against the urging of the spring 69R to a position for engaging a shifting surface 78' of the control member 75. Accordingly, during the next oscillatory movement imparted to the indexing pawls 57L, 57R, the indexing pawl 57R engages the shifting surface 78' of the control member 75 so as to pivot the control member 75 to the other alternate position for effecting the winding of the ribbon 11 onto the spool 27R. When the control memher 75 moves to the other alternate position, the other lock pawl 79R is moved into engagement with the ratchet teeth of the corresponding ratchet wheel 45R, and the indexing pawl 57R is urged into engagement with the ratchet wheel 45R for effecting rotational movement in an opposite direction. The other lock pawl 79L and the other indexing pawl 57L are both removed from engagement with the other ratchet wheel 47L by arm 77L, and the indexing pawl 57L will slide against the guide surface 778 provided by the other arm 77L upon further successive printing operations. Likewise, when the ribbon 19 becomes fully wound onto the spool 27R, the other tension arm 51L will effect a similar reversal through shifting surface 78 for winding the ribbon 19 back onto the ribbon spool 47L in a manner previously described.

What is claimed is:

1. In a ribbon feeding arrangement, the combination comprising:

first and second ratchet wheels supported for rotational movement for alternatively driving a pair of ribbon spools to wind a ribbon thereon,

first and second indexing pawls for rotatably indexing said first and second ratchet wheels in opposite rotational directions,

an oscillatable drive member for imparting a common oscillatable movement to said first and second indexing pawls for rotatably indexing said first and second ratchet wheels,

said first and second indexing pawls being movably supported on said oscillatable drive member for movement from indexing engagement with said first and second ratchet wheels respectively,

resilient biasing means for urging said first and second indexing pawls toward indexing engagement with said first and second ratchet wheels,

a control member having first and second arms for engagement with said first and second indexing pawls and being supported for movement to first and second alternate positions,

said first arm guiding said first indexing pawl from engagement with said first ratchet wheel upon movement of said control member to said second alternate position to enable rotational indexing of said second ratchet wheel by said second indexing pawl, and

said second arm guiding said second indexing pawl from engagement with said second ratchet wheel upon movement of said control member to said first alternate position to enable rotational indexing of said first ratchet wheel by said first indexing pawl,

a first lock pawl carried by said first arm for engagement with said first ratchet wheel upon movement of said control member to the first alternate position for preventing reverse rotational movement of said first ratchet wheel, and

a second lock pawl carried by said second arm for engagement with said second ratchet wheel upon movement of said control member to the second alternate position for preventing reverse rotational movement of said second ratchet wheel,

said control member being pivotally supported and having first and second shifting surfaces for engagement by said first and second indexing pawls,

a first tension member associated with said first ratchet wheel for sensing the tension of a ribbon being wound on a spool driven by said second ratchet wheel and being operable in response to increased ribbon tension for moving said first indexing pawl against the urging of said resilient biasing means for acting against the first shifting surface to effect movement of said control member to the first alternate position, and

a second tension member associated with said second ratchet wheel for sensing the tension of a ribbon being wound on a spool driven by said first ratchet wheel and being operated. in response to increased ribbon tension for moving said second indexing pawl against the urging of said resilient biasing means for acting against the second shifting surface to effect movement of said control member to the second alternate position.

l l l 

1. In a ribbon feeding arrangement, the combination comprising: first and second ratchet wheels supported for rotational movement for alternatively driving a pair of ribbon spools to wind a ribbon thereon, first and second indexing pawls for rotatably indexing said first and second ratchet wheels in opposite rotational directions, an oscillatable drive member for imparting a common oscillatable movement to said first and second indexing pawls for rotatably indexing said first and second ratchet wheels, said first and second indexing pawls being movably supported on said oscillatable drive member for movement from indexing engagement with said first and second ratchet wheels respectively, resilient biasing means for urging said first and second indexing pawls toward indexing engagement with said first and second ratchet wheels, a control member having first and second arms for engagement with said first and second indexing pawls and being supported for movement to first and second alternate positions, said first arm guiding said first indexing pawl from engagement with said first ratchet wheel upon movement of said control member to said second alternate position to enable rotational indexing of said second ratchet wheel by said second indexing pawl, and said second arm guiding said second indexing pawl from engagement with said second ratchet wheel upon movement of said control member to said first alternate position to enable rotational indexing of said first ratchet wheel by said first indexing pawl, a first lock pawl carried by said first arm for engagement with said first ratchet wheel upon movement of said control member to the first alternate position for preventing reverse rotational movement of said first ratchet wheel, and a second lock pawl carried by said second arm for engagement with said second ratchet wheel upon movement of said control member to the second alternate position for preventing reverse rotational movement of said second ratchet wheel, said control member being pivotally supported and having first and second shifting surfaces for engagement by said first and second indexing pawls, a first tension member associated with said first ratchet wheel for sensing the tension of a ribbon being wound on a spool driven by said second ratchet wheel and being operable in response to increased ribbon tension for moving said first indexing pawl against the urging of said resilient biasing means for acting against the first shifting surface to effect movement of said control member to the first alternate position, and a second tension member associated with said second ratchet wheel for sensing the tension of a ribbon being wound on a spool driven by said first ratchet wheel and being operated in response to increased ribbon tension for moving said second indexing pawl against the urging of said resilient biasing means for acting against the second shifting surface to effect movement of said conTrol member to the second alternate position. 